Heart valve

ABSTRACT

A heart valve prosthesis can be formed with a harvested tissue heart valve and a sewing rim that extends outwardly from the annulus of the harvested heart valve for easier attachment of the prosthesis. The heart valve prosthesis can further include a belt that extends along the annulus to provide further support to the valve annulus. A single piece of pericardial tissue can be used to form the sewing rim, belt and a collar that envelopes the edge of the annulus. The harvested heart valve prosthesis can have the diameter of its annulus adjusted using pledgeted suture prior to the application of additional support structures such as the belt, sewing rim and collar.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of copending U.S. patentapplication Ser. No. 09/475,525, now U.S. Pat. No. 6,409,759 to Peredo,incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The invention relates to prosthetic heart valves. Moreparticularly, the invention relates to prosthetic heart valves for thereplacement of damaged mitral or tricuspid heart valves.

[0003] Heart valve insufficiency can be a debilitating and possibly lifethreatening condition. For example, heart valve regurgitation, i.e.,backward leakage of blood at a heart valve, results in reduced pumpingefficiency. With respect to mitral valve regurgitation, compensatorymechanisms such as hypertrophy and dilation of the ventricle suggestearly treatment to prevent progressive deterioration of ventricularfunction. Diagnosis of mitral regurgitation can be performed usingvisualization with transesophageal echocardiography or byechocardiography. In particular, defective leaflet coaptation and thesite and direction of the regurgitant flow can be examined to evaluatelikely modes of failure.

[0004] Mitral valve prolapse, i.e., myxomatous degeneration of mitralvalve leaflets, is the most common cause of mitral regurgitation inNorth America. Rheumatic heart disease was the most common cause ofmitral regurgitation in the United States thirty years ago and is stillthe most common cause of mitral regurgitation in developing countries.Chronic rheumatic heart disease results in retraction, deformity andrigidity of one or both mitral valve cusps as well as structuralabnormalities in the commissures, chordae tendineae and papillarymuscles. Ischemic mitral regurgitation (IMR), i.e., anemia of the valvetissue due to reduced arterial blood flow feeding the valve tissue, isthe second most common cause of mitral valve regurgitation. Studiessuggest that annular irregularities and posterior papillary musclefibrosis with scarring of the underlying ventricular wall may beassociated with IMR.

[0005] Many cases of mitral regurgitation can be repaired bymodifications of the original valve in a procedure generally referred toas valvuloplasty. For example, one repair technique uses an annuloplastyring to provide structural support to the natural annulus of the nativevalve. For severe cases of heart valve damage, however, reconstructivevalvular surgery may not be possible. In such cases, valve replacementmay be required.

[0006] Physicians use a variety of prostheses to correct problemsassociated with the cardiovascular system, especially the heart. Forexample, the ability to replace or repair diseased heart valves withprosthetic devices has provided surgeons with a method of treating heartvalve deficiencies due to disease and congenital defects. A typicalprocedure involves removal of the native valve and surgical replacementwith a prosthetic heart valve.

[0007] Both mechanical heart valve prostheses and tissue based heartvalve bioprostheses have been used to replace damaged heart valves.Mechanical heart valves have the advantage of better durability, butpatients with mechanical heart valves generally are required to useanticoagulants throughout their lifetimes. Anticoagulants haveassociated risks, such as hemorrhages, embolism and thromboembolism.Tissue based bioprostheses do not require the long term use ofanticoagulants due to a lower incidence of thromboembolism.

SUMMARY OF THE INVENTION

[0008] In a first aspect, the invention pertains to a heart valveprosthesis comprising a harvested tissue heart valve with integralleaflets. The heart valve has an annulus at one end of the valve, and asewing rim extends outwardly from the annulus.

[0009] In another aspect, the invention pertains to additionalembodiments of a heart valve prosthesis comprising a harvested tissueheart valve with integral leaflets. The heart valve has an annulus atone end of the valve, and a belt secured around at least a substantialportion of an outer circumference of the annulus of the harvested tissueheart valve.

[0010] In a further aspect, the invention pertains to still furtherembodiments of a heart valve prosthesis comprising a harvested tissueheart valve with integral leaflets. The harvested tissue heart valve hasan annulus at one end of the valve, and pledgeted suture constricts aportion of the circumference of the annulus.

[0011] Moreover, the invention pertains to a method of producing a heartvalve prosthesis comprising a harvested tissue heart valve with integralleaflets, the heart valve having an annulus at one end of the valve, themethod comprising attaching a sewing rim extending outward from thesurface annulus of the harvested tissue heart valve.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a side perspective view of a harvested heart valve witha sutured annulus viewed along the posterior medial segment of theannulus.

[0013]FIG. 2 is a side perspective view of the harvested heart valve ofFIG. 1 viewed along the antero-lateral aspect of the annulus.

[0014]FIG. 3 is a side perspective view of the harvested heart valve ofFIG. 1 viewed along the posterior mitral annulus.

[0015]FIG. 4 is a top plan view of a harvested mitral valve exhibitingmitral valve insufficiency.

[0016]FIG. 5 is a top plan view of a harvested mitral valve wherein theleaflets close properly.

[0017]FIG. 6 is a side perspective view of a mitral heart valveprosthesis with a collar sewing rim and belt viewed along the posteriorside of the annulus.

[0018]FIG. 7 is a bottom perspective view of the mitral heart valveprosthesis of FIG. 6.

[0019]FIG. 8 is a side perspective view of the mitral heart valveprosthesis of FIG. 6 viewed from the anterior side of the annulus.

[0020]FIG. 9 is a top perspective view of the bioprosthetic valve ofFIG. 6.

[0021]FIG. 10 is a top plan view of the bioprosthetic valve of FIG. 6.

[0022]FIG. 11 is a side perspective view of a bioprosthetic heart valvewith a pericardial sheet being initially attached to the bioprostheticvalve.

[0023]FIG. 12 is a side perspective view of the bioprosthetic heartvalve of FIG. 11 wherein a portion of the pericardial sheet is fastenedto the valve.

[0024]FIG. 13 is a side perspective view of the bioprosthetic heartvalve of FIG. 11 wherein the pericardial sheet is fastened around thecircumference of the valve.

[0025]FIG. 14 is a side perspective view of the bioprosthetic heartvalve of FIG. 11, wherein the pericardial sheet is being sutured to thebioprosthetic heart valve.

[0026]FIG. 15 is a side perspective view of the bioprosthetic valve ofFIG. 14 wherein the pericardial sheet is being folded to form a collar.

[0027]FIG. 16 is a side perspective view of the bioprosthetic valve ofFIG. 15 wherein the pericardial sheet is further folded to form a sewingrim.

[0028]FIG. 17 is a side perspective view of the bioprosthetic valve ofFIG. 16 wherein the pericardial sheet is being sutured to secure thecollar.

[0029]FIG. 18 is a side perspective view of the bioprosthetic valve ofFIG. 17 wherein the collar is secured by suture applied around thecircumference of the valve.

[0030]FIG. 19 is a side perspective view of the bioprosthetic valve ofFIG. 18 wherein suture is being applied to the sewing rim.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0031] An improved replacement heart valve or bioprosthesis includes asewing rim extending from the annulus along a substantial portion of itscircumference and a support ring or belt positioned to support the baseof the annulus. The bioprosthesis generally is formed from a harvestedtissue heart valve with intact leaflets. In preferred embodiments, asingle structure, such as a piece of pericardial tissue, is used to forma collar over the valve annulus, the sewing rim and the belt. Also, thediameter of the annulus of the valve can be reduced using suture priorto the application of the collar. The resulting heart valvebioprosthesis corrects for dilation of the annulus following harvestingof the valve from a donor and reduces the risk of heart valveinsufficiency following implantation. “Bioprosthesis” is used in a broadsense to include bioprosthetic heart valves comprised of a naturalmaterial component that is joined together with other natural orsynthetic materials to manufacture the replacement heart valve.

[0032] The improved features of the bioprosthetic valves describedherein are suitable for use on atrio ventricular valves, i.e., mitralvalves and tricuspid valves, that are constructed using a harvestedtissue valve. The harvested valves can be treated appropriately prior toimplantation, as described further below. Generally, the bioprostheticvalves are stentless, i.e., a support stent is not used. While theimproved features are particularly advantageous for the production ofbioprosthetic atrio ventricular valves, at least the improved sewing rimfeature can be used advantageously with a bioprosthetic aortic valve.Aortic valves have a simpler structure without the presence of chordaetendineae.

[0033] The bioprosthetic valves can be formed using a procured orharvested homograft tissue valve, i.e., a valve from a donor of thepatient's species, or a xenograft tissue valve, i.e., a valve from adonor of a different species than the patient. Harvested mitral ortricuspid valves preferably include intact chordae tendineae attached toa portion of papillary muscle of the donor. Even though thebioprosthetic valves of the invention can be mitral valves or tricuspidvalves, the discussion below focuses on mitral valves. Mitral valvebioprostheses can be implanted into patient as a replacement for eithera mitral or tricuspid valve. Similarly, tricuspid valves incorporatedinto a bioprosthesis, in principle, can be used to replace damagedmitral or tricuspid valves. Preferably, prostheses formed from harvestedmitral valves are used to replace damaged mitral valves, and prosthesesformed from harvested tricuspid valves are used to replace tricuspidvalves.

[0034] In preferred embodiments, the harvested valves are processed tointroduce three improved features. First, the harvested valve is securedaround its circumference to reduce or maintain the diameter of theannulus. This reduction of the circumference corrects for expansion ofthe valve annulus that results due to the removal of native structuralsupport following the harvesting of the valve.

[0035] Second, a sewing rim is formed that extends outwardly from thesurface of the valve along the side of the annulus around thecircumference of the valve. By forming the sewing rim along the side ofthe annulus, the risk of damaging the leaflets during implantation byinserting the suture needle through the leaflets is decreased incomparison with using a collar located at the edge of the annulus as asewing cuff. The sewing rim can be formed from a portion of materialused in forming a collar that is folded over the edge of the annulus.

[0036] Third, a support ring or belt that is a functional equivalent ofan annuloplasty ring is constructed around the circumference along theside of the annulus to support the annulus of the valve followingimplantation. This belt may eliminate the need for using a separateannuloplasty ring when surgically implanting the valve. The belt can beconstructed from the same piece of material used to form the collar andsewing rim.

[0037] The collar, sewing rim and belt can be constructed from a varietyof natural and synthetic biocompatible materials. In a preferredembodiment, pericardial tissue is used to form the collar, sewing rimand belt. For example, the belt can be formed from rolled-up pericardialtissue at the end of a sheet of the pericardial tissue and the sewingrim can be formed from a piece of folded pericardial tissue between thebelt and the portion of tissue that is folded over the edge of theannulus to form the collar.

[0038] To form the preferred embodiments of the bioprosthetic heartvalves, the annulus of the harvested valve is sutured to draw in thecircumference and achieve the desired annular circumference prior toaddition of the collar, sewing rim and belt. After suturing the annulus,the collar, sewing rim and/or belt are attached to the sutured annulusof the harvested valve. If the collar, sewing rim and belt are formedfrom a single section of material, the procedure properly positions eachof the elements at the appropriate location on the tissue heart valve.Markings can be placed at suitable locations along the collar, sewingrim and/or belt to assist the physician with properly positioning andimplanting the valve during the implantation process.

[0039] Structure of Improved Heart Valve Bioprostheses

[0040] The improved heart valve bioprosthesis includes a procured orharvested natural heart valve that is modified before implantation. Atleast a portion of a supplemental support structure preferably supportsthe annulus of the harvested valve. The supplemental support structureis generally elastic and flexible with respect to the shape of theannulus while maintaining a desired circumference of the annulus. Thesupport structure generally extends around a substantial portion of thecircumference of the annulus, preferably at least a majority of thecircumference, and more preferably extends around the entirecircumference. For mitral and tricuspid valves, additional supports canbe used for the papillary muscle sections attached to chordae. The heartvalve bioprosthesis is stentless.

[0041] The supplemental support structure can be formed from natural orsynthetic materials, as described in detail below. The supplementalsupport structure can assist with the sizing and implantation of thebioprosthesis as well as improving the durability and performance of thebioprosthesis. To form a mitral or tricuspid heart valve bioprosthesis,a mitral or tricuspid heart valve structure is harvested from a donor.The procured heart valve prosthesis can be treated prior to additionalprocessing, as described further below.

[0042] Referring to FIGS. 1-3, harvested mitral heart valve 100preferably includes an annulus 102, leaflets 104, which connect toannulus 102, chordae tendineae 108 which extend between leaflets 104 andportions of papillary muscle 110 of chordal origin from the host animal.The leaflets 104, chordae 108 and chordal origin papillary muscle 110form a complete subvalvular apparatus. Annulus 102 includes a remainingportion of porcine aortic cusp 112 at the anterior mitral annulus 114.

[0043] Mitral heart valves often increase in valve diameter followingharvesting of the valve from the donor due to the lack of support forthe valve. Mitral annular enlargement takes place almost entirely in theregion of the posterior mitral annulus 116. Posterior mitral annulus 116is formed mostly with atrial muscle, while the region of anteriorannulus 114 is supported by the fibrous skeleton, i.e., mitro-aortictendinous tissue. Enlargement of the valve diameter can impair propervalve coaptation, as shown in FIG. 4, where leaflets 104 do not meetproperly or completely close in the center of the valve. Improperclosure of the valve can result in significant malfunctioning of thevalve, which can require valve replacement.

[0044] In preferred embodiments, the diameter of annulus 102 of valve100 is reduced prior to the addition of other support structures forannulus 102, such as with suture. While this suturing can be formed witha single piece of suture, it is preferred to form the sutured annuluswith a plurality of suture segments to avoid introducing excess tensionthat can result if a single suture is used. Also, it is preferred to usepledgeted, monofilament suture in which pledgets at each end of thesuture help to secure a section of suture under tension without damagingthe annulus. Other methods to draw in or reduce the diameter of theannulus can be used, such as clipping or stapling.

[0045] A particularly preferred embodiment is shown in FIGS. 1-3 wherethree sections of pledgeted, monofilament suture are used to reduce thediameter of the valve. Referring to FIG. 1, a first segment of suture130 with pledgets 132, 134 is placed on the lateral segmentcorresponding to the posterior medial segment of the annulus. Referringto FIG. 2, a second segment of suture 136 with pledgets 138, 140 isplaced along the antero-lateral aspect of annulus 102. Referring to FIG.3, a third segment of suture 142 with pledgets 144, 146 is placed alongthe posterior mitral annulus 116. A running or continuous suture can beused, for example, in the suture placement. Appropriate reduction of thevalve diameter results in proper valve leaflet coaptation, i.e., fullmitral valve leaflet closure, at leaflet junction 148, as shown in FIG.5. Leaflet coaptation can be observed during the suturing process toensure that proper tension is applied to result in correct coaptation.Furthermore, with harvested valve 100 having an adjusted diameter, thephysician can directly size the valve for implantation into the patient.

[0046] While the valve diameter preferably is reduced using suture, asdescribed above, excessive manipulation of the valve during implantationcan result in enlargement of the valve diameter due to deterioration ofthe effectiveness of the suture. Thus, a collar preferably is appliedover the valve annulus to further maintain the valve annulus at theproperly selected annulus diameter. The pledgeted suture sewn into theannulus to reduce the valve diameter and the collar together create astable and durable valve bioprosthesis with an appropriately sizedannulus.

[0047] An annulus collar has been used to reduce the annular diameter,as described in U.S. Pat. No. 5,733,331 to Peredo, entitled “TotalMitral Heterologous Bioprosthesis to be Used in Mitral or TricuspidHeart Replacement,” incorporated herein by reference. The use ofpledgeted suture sewn directly into the annulus combined with an annularcollar and belt, however, offers significant advantages. First, thepledgeted suture can be used conveniently to distribute the desiredtension to provide a competent valve. In addition, the belt and collarprovide added protection against undesirable enlargement of the valvediameter prior to and after implantation.

[0048] As noted above, along with an annulus collar, a preferred heartvalve bioprosthesis has a sewing rim along the side of the annulus and abelt supporting the base of the annulus. A preferred heart valvebioprosthesis 160 is shown in FIGS. 6-10. Mitral valve bioprosthesis 160includes a collar 162, a sewing rim 164 and a belt 166 secured over theannulus 102 of the harvested mitral valve. Although collar 162, sewingrim 164 and belt 166 can be applied individually or with two of theelements formed together, in preferred embodiments, collar 162, sewingrim 164 and belt 166 form a single, unified supplemental supportstructure 168 at annulus 102. The diameter of the valve bioprosthesis isselected to obtain proper closure of the leaflets, as shown in FIG. 10.

[0049] Collar 162 envelops the edge of annulus 102, being secured withsuture both on the inside of annulus 102 and the outside of annulus 102.Sewing rim 164 includes an extension of material extending outwardly,preferably generally perpendicular, from the surface of annulus 102.Sewing rim 164 can be formed, for example, from a fold of material, asdescribed further below. Sewing rim 164 generally extends at least about2 mm from the surface of the annulus, preferably from about 2 mm toabout 4 mm, and more preferably from about 2 mm to about 3.5 mm from thesurface of the annulus. The sewing rim preferably has a thickness lessthan about 2 mm, and preferably from about 1.3 mm to about 1.8 mm.

[0050] Belt 166 is a strong, relatively resilient structure, whichobviates the need for the implantation of a separate annuloplasty ring.Belt 166 eliminates valve dilation and changes in diameter, andmaintains competency of the valve following implantation. Belt 166 canbe formed from rolled up material, or from a fold of material covering aflexible ring structure, such as a polymer ring or metal wire, to formbelt 166, or from the separate attachment of a belt structure.

[0051] Belt 166 can have any reasonable cross sectional shape, such asround or rectangular, and the cross sectional shape can vary from oneportion of the belt to other portions of the belt. Belt 166 generallyhas a thickness or distance “d” along the surface of the annulus, asshown in FIG. 8, of at least about 1.5 mm, preferably from about 1.5 mmto about 4 mm and more preferably from about 2 mm to about 3 mm.Similarly, belt 166 generally extends outwardly from the annulus surfaceat least about 1.5 mm, preferably from about 1.5 mm to about 4 mm andmore preferably from about 2 mm to about 3 mm.

[0052] To assist the surgeon with correct placement of the heart valveduring implantation, a marker 180 can be placed at the mid-position ofthe posterior mitral annulus, as shown in FIGS. 6, 9 and 10. Marker 180can be made, for example, with suture. Similarly, markers 182 can beplaced to denote each trigone, as shown in FIGS. 8-10. Markers 182should be visually distinguishable from marker 180, for example, by theuse of different colors and/or by the use of a different shape, such asan “x” for the trigone markers 182. The trigone markers can be used bythe surgeon to guide the attachment of the heart valve bioprosthesis tothe patient's annulus during implantation.

[0053] Further structural support can be provided with strips 190 thatconnect annulus 102, support structure 168, or a component of supportstructure 168, with one of the chordal origin papillary muscles sections110. Strips 190 decrease the stress on chordae 108 during the attachmentprocedure. Strips 190 generally are attached in a way that maintains thenatural angulation and spacial geometry between the papillary musclesections 110 and chordae 108. Strips 190 are of an appropriate length tomaintain a uniform chordal tension such that the stress load isdistributed between strips 190 and chordae 108 to increase valvedurability. In preferred embodiments, a plurality of strips 190 are usedwith each chordal group. As shown in FIGS. 6-8, a total of four strips190 are used, with two strips 190 used for each of the two chordalgroups.

[0054] In preferred embodiments, natural chordae groups are preservedwhere each group is secured to one or more sections of chordal originpapillary muscle 110. Papillary muscle 110 can be secured in groups withan upper patch 196 and a lower patch 198. The edges of lower patch 198preferably fold over the edges of upper patch 196. Upper patch 196 iscut-out such that upper patch 196 does not contact the chordae 108.Thus, upper patch 196 does not disrupt the attachment of chordae 108with papillary muscle 110. Upper patch 196 preferably is sutured tolower patch 198 through papillary muscle 110 to form a secure structurefor attachment to the papillary muscle of the patient duringimplantation. Strips 190, upper patch 196 and lower patch 198 each canbe made from tissue, such as a pericardial tissue, or from syntheticmaterial.

[0055] Materials for Forming the Heart Valve Bioprosthesis

[0056] As described in the previous section, a preferred heart valvebioprosthesis includes a harvested natural heart valve, suture,pledgets, a collar, a belt, a sewing rim, strips connecting the annulussupport structure with the chordal origin papillary muscles and patchesattached to papillary muscle sections of the harvested valve. Except forthe harvested natural heart valve, the remaining materials can be eithernatural or synthetic. The harvested tissue heart valve can be ahomograft valve, i.e., from the same species as the patient, or axenograft valve, i.e., from a different species than the patient. Thus,for a human patient, a homograft heart valve is removed from a humancadaver. Suitable xenograft mitral heart valve structures for humanpatients can be, for example, bovine, porcine, canine, seal, kangaroo orfrom transgenic mammals. Suitable donors have a heart valve of anappropriate size and shape.

[0057] Harvested tissue heart valves can be fixed by crosslinking. Thisprovides mechanical stabilization, for example, by preventing enzymaticdegradation of the tissue. Crosslinking also removes antigenic sitesthat could result in the patient's rejection of the bioprosthesis.Glutaraldehyde or formaldehyde typically is used for fixation, but otherfixatives can be used, such as epoxides, genipin and other difunctionalaldehydes. Xenografts, i.e., prostheses incorporating tissue from aspecies different from the patient's species, generally are fixed priorto use. Homografts or allografts, i.e., prostheses incorporating tissueof a different individual of the patient's species, may or may not befixed prior to use. In addition, the bioprostheses can be treated toreduce calcification and/or the risk of microbial infection, and canincorporate other features of tissue engineering.

[0058] As noted above, preferred embodiments of the heart valvebioprosthesis include pledgeted suture that secures the diameter of thevalve annulus to a diameter approximating the native state. Suitablesuture can be formed from biological sources, such as cat gut suture andnatural fibers such as cotton and silk, or synthetic materials, such assynthetic polymers. The suture can be mono-filament suture, such as catgut and Prolene®, or braided (poly-filament suture), such as natural orsynthetic fibers formed into yarns. The suture can be absorbable orpermanent. The suture preferably comprises permanent monofilamentsuture, such as Prolene® brand polypropylene suture, which is relativelynonabrasive to tissue.

[0059] Pledgets function as an anchoring device in pledgeted suture ateach end of the suture. The pledgets help to protect the sutured tissuefrom tearing. The pledgets can be formed from natural or syntheticmaterials. Preferred pledgets are formed from crosslinked pericardialtissue. While any reasonable size of pledgets can be used, 2 mm×4 mmpledgets are a convenient size.

[0060] As noted above, the collar, sewing rim and belt preferably areproduced from a single piece of material. The collar, sewing rim andbelt can be produced from natural material, synthetic material, or acombination thereof. Preferred material for the production of a collar,sewing rim and belt includes harvested tissue, and more preferablypericardial tissue. The pericardial tissue section generally isxenograft tissue, especially bovine tissue, that is fixed bycrosslinking.

[0061] The pericardial tissue or other biocompatible material section iscut to have the desired size to form the collar, sewing rim and belt.Due to varying valve sizes, the biocompatible material section can havea range of sizes with height ranging from about 1 cm to about 2 cm,length ranging from about 3 cm to about 12 cm and thickness ranging fromabout 0.2 mm to about 0.9 mm. The length of the section corresponds tothe circumference of the heart valve bioprosthesis following attachmentof the material. The height of the biocompatible material section isused to form the collar, sewing rim and belt.

[0062] Using a single sheet of pericardial tissue, one long edge of thepericardial tissue can be rolled to form the belt structure of theultimate bioprosthesis. The tissue preferably is rolled between two andfour times, such that the total thickness of the belt ranges from aboutfour times to about 8 times the thickness of a sheet of tissue.Referring to FIG. 11, a section of pericardial tissue 200 includes aportion of rolled tissue 202. Rolled tissue 202, forming a belt, is keptin its rolled configuration by interrupted or continuous mono ormultiple filament suture 204.

[0063] The sewing rim can be formed during the process of securing thetissue to the valve, as described below. The edge of the tissue oppositethe belt is folded over the end of the annulus to form the collar.

[0064] As noted above, the papillary muscle patch, pledgets, collar,sewing rim and belt each can be formed from synthetic material, such asnatural or synthetic polymers. Polymeric materials can be fabricatedfrom synthetic polymers as well as purified biological polymers. Thepolymeric materials can be formed into fibers or yarns and then woveninto a mesh to form a sheet or other shape. Alternatively, the polymermaterials can be molded or cast into appropriate forms.

[0065] Appropriate synthetic polymers include, without limitation,polyamides (e.g., nylon), polyesters, polystyrenes, polyacrylates, vinylpolymers (e.g., polyethylene, polytetrafluoroethylene, polypropylene andpoly vinyl chloride), polycarbonates, polyurethanes, poly dimethylsiloxanes, cellulose acetates, polymethyl methacrylates, ethylene vinylacetates, polysulfones, nitrocelluloses and similar copolymers.

[0066] Biological polymers can be naturally occurring or produced invitro by, for example, fermentation and the like. Purified biologicalpolymers can be appropriately formed into a substrate by techniques suchas weaving, knitting, casting, molding, extrusion, cellular alignmentand magnetic alignment. Suitable biological polymers include, withoutlimitation, collagen, elastin, silk, keratin, gelatin, polyamino acids,polysaccharides (e.g., cellulose and starch) and copolymers thereof.

[0067] As noted above, multiple portions of one or more biocompatiblematerials can be used to form the collar, sewing rim and belt. Two ormore portions can be attached together prior to securing the portions tothe harvested heart valve. For example, a ring or the like can befastened, for example with suture, to or in a pericardial sheet to forma belt. The ring can be formed from natural material, i.e., tissue, orsynthetic material. The pericardial sheet can then be used to form thecollar and sewing rim. The ring is positioned along the pericardialsheet such that it will be located at a desired position for the beltonce the components are assembled. For example, the belt can preferablybe placed near the bottom long edge of the pericardial sheet such thatthe belt is located just below the sewing rim after the components areassembled. Similarly, the belt can be fastened near the center of thepericardial sheet such that the belt will be located just above thesewing rim after components are assembled.

[0068] Alternatively, the portions can be secured together whenattaching the components to the bioprosthesis. A particular componentcan be sewn to another securing component or directly to the harvestedheart valve. For example, a sheet of material can be used to form thecollar and sewing rim while an annular structure used for the belt canbe sewn directly to the tissue of the harvested heart valve, directly tothe material forming the collar and sewing rim, or a combinationthereof. Similarly, the collar and sewing rim can be formed fromdifferent portions of material, which are attached together orseparately secured to the annulus of the harvested heart valve.

[0069] Strips are generally connected between the annulus supportstructure and the papillary muscle section or corresponding patches.These strips can be formed from natural materials, such as tissue, orsynthetic materials, such as polymers. The strips can be attached to theannulus support structure or to the harvested heart valve.

[0070] The papillary muscle patches can be formed from one or morematerials. For example, an upper patch can be formed from one materialwhile a lower patch can be formed from a second material. Similarly, asingle papillary muscle patch can be formed from a combination ofmultiple materials. While papillary muscle patches are preferably formedfrom tissue, such as fixed bovine pericardial tissue, papillary musclepatches can be formed from synthetic materials, as described above, or acombination of tissue and synthetic materials.

[0071] Formation of the Improved Heart Valve Bioprosthesis

[0072] The preferred heart valve bioprosthesis includes pledgeted suturesewn around the annulus of the harvested tissue heart valve. As notedabove, it is preferable to use multiple sections, for example threesections, of pledgeted suture to distribute the tension around thecircumference of the annulus. The pledgeted suture can be applied byhand where the degree of reduction of the valve circumference isdetermined by the degree of tension applied with the suture. The amountof tension should result in a competent valve. The suturing process isperformed in a way to avoid tissue damage by the suture used to decreasethe extent of a particular segment of the valve annulus. The protectiongiven by a bovine pericardial pledget is generally sufficient to preventtissue laceration by the suture material.

[0073] The application of the collar, sewing rim and belt is describedin terms of attachment of an integral section of biocompatible material,such as pericardium, that forms all three structures. Approaches for theattachment of alternative structures for formation of the collar, sewingrim and belt can be readily adapted from the following description ofthe attachment of a single piece of bovine pericardium. Referring toFIG. 11, a section of pericardium 200, such as bovine pericardialmaterial, is positioned relative to harvested tissue heart valve 206such that strips 208 can be positioned near a group of chordae. Strips208 are secured to a fragment or fragments of papillary muscle 210 fromthe transplant donor or to patches 212 supporting papillary muscle 210.Preferably, a first edge 214 of bovine pericardial material 200 ispositioned approximately in the middle of the posterior annulus. Patches212 for providing additional support can be secured to the papillarymuscle fragment(s) 210 prior to or after securing strips 208 topapillary muscle fragments 210.

[0074] Suture 220 is applied to tack pericardial material 200 at thecorrect location with strips 208 positioned appropriately near chordae216 for attachment to papillary muscle fragments 210 and/or patches 212,as shown in FIG. 12. Pericardial material 200 is wrapped around theremaining portion of the valve circumference and secured with additionalsuture 222, as shown in FIG. 13. The edges of the pericardial tissue 200meet at a seam 224. The edges preferably meet essentially flush, forminga seam 224, although seam 224 can be used to adjust the joining of theedges. When the pericardial material 200 is positioned around thecircumference of harvested tissue heart valve 206, a second group ofstrips 226 are positioned for attachment to papillary muscle 210associated with a second group of chordae 218.

[0075] Referring to FIG. 14, pericardial material 200 is attached aroundthe entire annulus with continuous or interrupted sections of mono ormultiple filament suture 228. Preferably, the suture is applied justabove the belt 202 such that the sewing rim can be formed above thebelt. Suture 228 preferably passes through pericardial material 200 andthe annulus of harvested tissue valve 206, avoiding the leafletmaterial.

[0076] The remaining pericardial material 200 is folded to form thecollar and sewing rim. Referring to FIGS. 15 and 16, the top portion 240of pericardial material 200 is used to form the collar 242. A portion ofmaterial 244 between collar 242 and suture 228 is folded to form thesewing rim 246, as shown in FIG. 17.

[0077] Collar 242 is secured with suture 248. To complete the stitching,suture 248 is passed from the outer edge 249 of collar 242 through theannulus of harvested tissue valve 206 through the inner edge 253 ofcollar 242, as shown in FIG. 17, although suturing could be doneseparately on both inner edge 253 and outer edge 249. Suturing iscontinued around the circumference of the valve with one or moresections of suture 248 to complete formation of collar 242, as shown inFIG. 18.

[0078] To complete formation of sewing rim 246, one or more sections ofsuture 250 are sewn through the inner edge 251 of sewing rim 246.Preferably, suture 250 passes from top surface of sewing rim 246 throughthe bottom surface of sewing rim 246, as shown in FIG. 19. Suture 250generally goes around the whole circumference of sewing rim 246. Thiscompletes the formation of the collar 242, sewing rim 246 and belt 202structures on the heart valve bioprosthesis 252. In some embodiments,sewing rim 246 is positioned around the entire circumference of valve206, and collar 242 and belt 202 can be around less than the entirecircumference, if desired.

[0079] Storage, Distribution and Use of Bioprosthesis

[0080] Following formation of the heart valve bioprosthesis, thebioprosthesis can be stored. The bioprosthesis generally is stored in amoist environment such that the tissue components do not become driedout. The tissue can undergo irreversible degradation if it becomes driedout. In preferred storage approaches, the bioprosthesis is immersed in aliquid during storage.

[0081] Preferred storage techniques minimize the risk of microbialcontamination. For example, the biocompatible material can be stored ina sealed container with sterile buffer and/or saline solution. Eventhough the bioprosthesis is stored in a sterile environment, the storagetime can be limited appropriately to keep any possible degradation ofthe bioprosthesis with the passage of time to acceptable levels.

[0082] For distribution, the bioprosthesis generally is placed in sealedand sterile containers. The containers can be dated such that the datereflects the maximum advisable storage time accounting for possibledeterioration of the heart valve bioprosthesis. The containers generallyare packaged with instructions for the implantation of the heart valvebioprosthesis along with desired and/or required labels. The containersare distributed to health care professionals for surgical implantationof the prostheses. The implantation is performed by a qualified healthcare professional. The surgical implantation generally involves thereplacement of damaged tissue with the bioprosthesis.

[0083] As noted above, in preferred embodiments, an annuoplasty ring isnot needed since the belt is secured about the circumference of thereplacement valve annulus. Sizing can be performed, as with anyprosthetic valve, by comparing the sewing rim to the patient's nativeannulus. The improved valves described herein are particularlyconvenient for implantation without risking damage to delicate leafletsand for maintaining valve compentency.

[0084] The embodiments described above are intended to be illustrativeand not limiting. Additional embodiments are within the claims below.Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A heart valve prosthesis comprising: a harvestedtissue heart valve with integral leaflets, the heart valve having anannulus at one end of the valve; and a belt secured around at least asubstantial portion of an outer circumference of the annulus of theharvested tissue heart valve.
 2. The heart valve prothesis of claim 1wherein the belt has a thickness along the annulus surface from about 2mm to about 3 mm.
 3. The heart valve prosthesis of claim 1 wherein thebelt has a thickness along the annulus surface of at least about 1.5 mm.4. The heart valve prosthesis of claim 1 wherein the belt has athickness along the annulus surface of at least about 2 mm.
 5. The heartvalve prosthesis of claim 1 wherein the belt comprises rolled up tissue.6. The heart valve prosthesis of claim 1 wherein the belt comprisespericardial tissue.
 7. The heart valve prosthesis of claim 1 wherein thebelt comprises pericardial tissue folded over a ring structure.
 8. Theheart valve prosthesis of claim 1 wherein the belt comprises syntheticmaterial.
 9. The heart valve prosthesis of claim 1 wherein the beltextends outwardly from the annulus surface from about 1.5 mm to about 4mm.
 10. The heart valve prosthesis of claim 1 wherein the belt extendsoutwardly from the annulus surface from about 2 mm to about 3 mm. 11.The heart valve prosthesis of claim 1 wherein the harvested tissue heartvalve comprises a harvested xenograft mitral heart valve.
 12. The heartvalve prosthesis of claim 11 wherein the harvested xenograft mitralheart valve is harvested from a mammal with a heart valve having a sizeand anatomy similar to a human's size and anatomy.
 13. The heart valveprosthesis of claim 11 wherein the harvested xenograft mitral heartvalve has intact chordae extending from the leaflets and a section ofpapillary muscle attached at the end of the chordae.
 14. The heart valveprosthesis of claim 13 wherein the papillary muscle attached to thechordae is reinforced with a reinforcing patch.
 15. The heart valveprosthesis of claim 1 further comprising a collar enveloping the end ofthe annulus of the harvested tissue heart valve.
 16. The heart valveprosthesis of claim 15 wherein the collar comprises xenograftpericardial tissue.
 17. The heart valve prosthesis of claim 16 whereinthe collar is sutured to the inner surface of the annulus and the outersurface of the annulus.
 18. The heart valve prosthesis of claim 15wherein the collar comprises tissue.
 19. The heart valve prosthesis ofclaim 15 wherein the collar and belt are formed from a single section ofintegral material.
 20. The heart valve prosthesis of claim 19 whereinthe integral material comprises pericardial tissue.
 21. The heart valveprosthesis of claim 1 wherein the annulus comprises pledgeted suturereducing the circumference of the annulus.
 22. The heart valveprosthesis of claim 1 further comprising a sewing rim that projects atleast about 2 mm from the surface of the annulus.
 23. The heart valveprosthesis of claim 22 wherein the sewing rim extends from about 2.0 mmto about 4 mm from the surface of the annulus.
 24. The heart valveprosthesis of claim 1 wherein the harvested tissue heart valve compriseshomograft tissue.
 25. A heart valve prosthesis comprising: a harvestedtissue heart valve with integral leaflets having an annulus at one endof the valve; and pledgeted suture constricting a portion of thecircumference of the annulus.
 26. A method of producing a heart valveprosthesis comprising a harvested tissue heart valve with integralleaflets, the heart valve having an annulus at one end of the valve, themethod comprising attaching a belt around at least a substantial portionof an outer circumference of the annulus of the harvested tissue heartvalve.
 27. The method of claim 26 wherein the belt has a thickness alongthe annulus surface of at least about 1.5 mm.
 28. The method of claim 26wherein the belt is formed from a rolled-up portion of pericardialtissue, the pericardial tissue extending to a collar that envelopes theend of the annulus.
 29. The method of claim 26 wherein the belt isformed by folding pericardial tissue over a ring structure.